It is known to operate a mass transit vehicle in conjunction with an automatic vehicle control system for providing speed and position control signals and to operate the passenger doors of such a vehicle with suitable door command signals. It is necessary to sense when the vehicle has stopped at a station platform before the door open signal causes the doors to open for the exit and entry of passengers. In addition, as described in a published article entitled "Automatic Train Control Concepts Are Implemented By Modern Equipment" by R. C. Hoyler at pages 145 through 151 of the Westinghouse Engineer for September, 1972, the vehicle door controls can be interlocked with vehicle zero speed detection to prevent automatic door opening before the vehicle has come to a stop.
A prime requirement of transit expressway and rapid transit vehicle door operation is that each door should be mechanically locked in a closed position before the vehicle is allowed to move along the track. Present mass transit vehicle door control systems employ either a lock subsystem consisting of a locking bar, unlocking force source and interlocks to maintain the locked state which is mechanically independent of the prime door opening force, or a rotary motion apparatus to close the door and the traveling overcenter of a toggle mechanism to lock the door.